The consumption of dietary fat causes the level of fat (triglyceride) in the blood to increase. It is hypothesized that a high fat diet may promote the development of atherosclerosis ("hardening of the arteries") in part because of the associated post-meal rise in the blood fat level. In this study, the investigators will compare the impact of high and very low fat diets on the atherogenicity (capacity to cause atherosclerosis) of postprandial fat particles.